The present invention relates to the consolidation of normal ambient room ventilation exhaust with that of special point or work site location exhaust requirements so that exhaust operations conveniently can be handled with a single fan unit rather than with two separate fans associated each with a specific one of such requirements.
Many commercial and/or industrial operations are carried out in work spaces which present the dual requirement of maintaining a continuous circulating in-flow and out-flow of ventilation or ambient air to the space (air change cycle) as well as capability for effecting rapid exhausting of gases liberated at a local work site in the space and evolving incident a particular industrial operation. These evolved gases can be of wide description as to type inclusive of simply being heated air or water vapor, or they may be industrial operation by-products which may constitute air pollutants and/or contaminants, etc. Effective removal of these gases directly at the site is desirable both from the standpoint of worker comfort and reduced exposure to pollutants. Patents which disclose aspects of point exhaust in a room space at plural locations and with one or more movable or flexible exhaust ducts is disclosed, for example, in U.S. Pat. Nos. 2,162,019; 2,347,334; 2,436,508; 2,604,840; 2,733,668; 3,368,474; 3,473,462; 4,086,847 and 4,446,861.
It has been commonplace in the past to meet the dual need of exhausting a room space and a localized work site by use of two separate exhausting arrangements. Thus, a first fan and associated duct work has been employed to remove space ambient air as part of the regular air change operation. Exhaust from a given work site on the other hand has been effected with a second duct arrangement and exhaust fan. In meeting the air change cycle needs, the ambient exhaust fan unit will operate on a continuous basis while the work site exhaust fan will operate on an intermittent basis, although, in some circumstances it too may be operated continuously. The situations where a particular gas is liberated at a work site may occur only at spaced time intervals. Thus operation of the gas removal fan unit on a continuous basis is wasteful of energy and adds unnecessary wear to the fan and its component parts. It is desirable therefore that a more effective, economical and simpler manner and apparatus arrangement be provided for exhausting a room space environment as well as when required, localized areas at work sites within the room space. Such exhaust arrangement also should effectuate rapid point exhaust with employment of speeded-up gas removal obtained with higher fan speed than that required for normal air change cycle purposes.